Project Summary/Abstract Systemic sclerosis-associated interstitial lung disease (SSc-ILD) affects approximately 80% of patients, induces overwhelming morbidity and is one of the leading causes of death in SSc. There is a distinct need for a systematically developed SSc-ILD response index that captures physiologic, radiologic, and patient-reported outcome measures. Under the Outcome Measures in Rheumatology (OMERACT) aegis, the investigators have received an endorsement on final domains for development of a SSc-ILD response index. The Principal Investigator (PI) now proposes a data-driven approach to validate that core set of items into a response index for SSc-ILD. Our central hypothesis, formulated and based on the expertise of the investigators and our preliminary data, is that a core set of variables can be used to develop a robust SSc-ILD-specific response index that spans the full range of relevant outcomes, including physiologic, radiographic and patient- reported measures. The PI will test the hypothesis by pursuing the following two specific aims: 1. Perform a prospective longitudinal observational clinical study to define a reliable, valid and responsive set of SSc-ILD measures for a combined response index, based on a recently completed consensus exercise, and 2. Employ prospective, data-driven, consensus-building techniques to develop and quantitatively evaluate candidate definitions for a response index for SSc-ILD. This proposal utilizes the expertise of the PI, an established clinical investigator in rheumatology, with experts in pulmonary medicine and radiology as co-investigators. In addition, he has gathered distinguished international researchers as the steering committee members.